The present invention generally relates to a push-button switch and more particularly, to an improved switch mechanism for a push-button switch.
Conventionally, there has been known a push-button switch, for example, as shown in FIG. 1, which generally includes a casing 1, a push-button 2 movably provided at the upper end portion of the casing 1, an operating member 3 provided in the casing 1 for vertical movement together with the push-button 2, and a switch mechanism accommodated in the lower end portion of said casing 1. The switch mechanism referred to above is constituted by a base member 4, a normally closed terminal 5, a normally open terminal 6 and a common terminal 7 which all are fixed to said base member 4, a rotary member 8 pivotally provided on the base member 4, a movable piece 9 journalled at its one end in the common terminal 7, and a reversing spring 10 fixed, at its one end, to the rotary member 8, and engaged, at its other end, with said movable piece 9. Thus, upon depression of the push-button 2 so as to rotate the rotary member 8 in the counterclockwise direction through the operating member 3, the movable piece 9 is adapted to be reversed or directed downwardly.
The known switch mechanism as described so far, however, has such a problem that electric current flowing through the journalled portion of the movable piece 9 in the common terminal 7 produces heat at such journalled portion, since the common terminal 7 and the movable piece 9 are subjected to a linear contact or point contact with each other, thus providing an extremely small area for the current to pass therethrough. Moreover, there has also been a disadvantage in that, when it is intended to reduce the size of the push-button switch of the above described type, the contact gap between the movable piece 9 and the normally open contact or normally closed contact is inevitably reduced, thus resulting in deterioration of insulating characteristics, etc.